This proposal is a collaborative, multi-disciplinary program involving researchers at the Department of Bioengineering and the Department of Mechanical Engineering University of Washington. Our objective is to develop resonant fiber-optic scanners and novel miniature imaging devices capable of optical beam focusing and high-speed 2-D beam scanning. The imaging device can integrate beam delivery, collection, focusing, and scanning into a highly compact single unit, making the device mountable on awake subjects to perform imaging at natural physiological conditions or endoscopically deliverable for imaging internal organs. Development of a technology that enables in vivo imaging of biological tissues at or near cellular level in real time could permit diagnosis of diseases at early stages, precision guidance of surgical interventions and monitoring of localized physiological functions. Optical coherence tomography (OCT) and confocal microscopy are capable of real time imaging of biological tissues at or near cellular level. In vivo and endoscopic applications of OCT and confocal microscopy require a novel scanner to perform beam scanning. The hypothesis of this research is that miniature OCT and confocal imaging devices can be developed using novel fiber-optic scanners. The fiber scanner also permits integration of OCT with confocal microscopy for improving imaging resolution when high numerical aperture optics are used. The specific aims of this exploratory proposal are: 1) to develop a piezoelectric-actuated, single optical fiber scanner that resonates at its first mode and scans the optical beam. We will investigate the feasibility of a miniature scanning microscope based on the fiber scanner for real time OCT/confocal imaging; 2) to develop a fiber scanner resonating at its second mode, and investigate the feasibility of an OCT/confocal imaging catheter/endoscope that employs the fiber scanner to perform beam scanning and focusing without the need for extra optical and mechanical components. We will characterize the performance of the miniature imaging devices using phantoms to critically evaluate the design and engineering issues of the fiber scanner based imaging probes. If successful, this technology could enable a new generation of miniature imaging devices.